In answer to your question, Richard; I have British citizenship and would like to start work as a freelance digital artist as soon as I move to Zurich in August. I thought this meant registering myself as a Sole Trader (selbständig/Einzelfirma?), which would be with AHV. I guess this is done some other way?

Again, many thanks for your help!
Chris

Yes indeed which is not the same as registering with the handelsamt ie company register. You hold up your hand in the middle of the street and shout yippeee I am self employed and indeed you are. To ensure you make all your contributions you then need to register with the AHV. That is no need to register your company as you will be a sole trader although you can.